Lim f(x+h)-f(x)/h untuk f(x)=x^2-4x, h mendekati 0

f(x) = x² - 4x

f(x + h) = (x + h)² - 4(x + h)
f(x + h) = x² + 2xh + h² - 4x - 4h

lim (h-->0) (f(x + h) -f(x))/h
= lim (h-->0) (x² + 2xh + h² - 4x - 4h - (x² - 4x))/h
= lim (h-->0) (2xh + h² - 4h)/h
= lim (h-->0) (2x + h - 4)
= 2x + 0 - 4
= 2x - 4